| Lutein is a hydrophobic carotenoid with multiple health care functions.However,its structural properties lead to poor stability and low bioavailability,which limits its application.Oil-in-water(O/W)emulsions are widely used to deliver lipophilic bioactive compounds in various products,which can overcome these limitations of lutein.Compared with ordinary emulsions,high internal phase emulsions(HIPEs)have excellent resistance to physical,chemical,microbial,and environmental conditions.HIPEs is defined as a highly concentrated emulsion system.Its controllable viscoelastic properties benefit from a minimum volume of more than 74%of the dispersed phase.In the traditional preparation methods of high internal phase emulsions,inorganic particles or synthetic surfactants are usually used for stabilization,but the addition of such stabilizers will harm human health.In recent years,biopolymers as stabilizers to replace traditional stabilizers have become the research hotspot.Hydrogel is a gel-like substance made of hydrophilic polymer and containing more than 90%water.It has a stable three-dimensional polymer network and is hydrophilic.It has a wide range of applications in a variety of industries.However,there is currently no research on using natural polymer-based hydrogels as emulsifiers to prepare high internal phase emulsions or encapsulating lutein with hydrogels.In this paper,lysozyme amyloid fibril-EGCG hydrogels were used as emulsifiers to stabilize the high internal phase emulsion for the first time,and its structure was characterized.Among them,egg white lysozyme(HEWL)and EGCG have a wide range of sources.Lysozyme amyloid fibrils and EGCG can be combined into hydrogels through supramolecular self-assembly,which belongs to the nanometer scale.The assembly process does not need to add a crosslinking agent,and the production is convenient and green.Afterward,lutein was embedded in a high internal phase emulsion stabilized by lysozyme amyloid fibril-EGCG hydrogels,and the structure of the high internal phase emulsion containing lutein was characterized.In addition,the anti-oxidation effect of the high internal phase emulsion stabilized by lysozyme amyloid fibril-EGCG hydrogels on functional oils is also studied,which provides a reference for constructing a food-grade lutein delivery system.Finally,the effects of ultraviolet light,temperature,Fe3+,and hydrogen peroxide treatment on the stability of lutein embedded in the stable high internal phase emulsion of lysozyme amyloid fibril-EGCG hydrogels were also investigated.1.Preparation and characterization of HIPEs stabilized hydrogelsExplore the effects of different EGCG concentrations and different amyloid fibrils concentrations on the particle size,Zeta potential,rheological properties,and microstructure of hydrogel-stabilized HIPEs.The experimental results show that the emulsion has solid rheological properties.With the increase of EGCG concentration and amyloid fibrils concentration,the viscoelastic modulus of the emulsion increases,and the maximum shear stress that can also be withstood increases;all conditions in this chapter,the particle size of the emulsion below is uniformly distributed,and all have a highly stacked multi-faceted geometry.In the lower EGCG concentrations(0 mg/mL-5 mg/mL),the average particle size of the emulsion decreases with the increase of EGCG concentration.In the laser confocal,the droplet size is also observed to become smaller and more densely packed.In the range of higher EGCG concentrations(5 mg/mL～20 mg/mL),the average particle size of the emulsion increases with the increase of EGCG concentration.The droplets tend to be round in laser confocal,and partial coagulation occurs.The average particle size of the emulsion decreases with the increase of amyloid fibrils,and the emulsion is observed in laser confocal.The droplet size becomes smaller,and the network structure becomes tighter.There was no significant difference in the Zeta-potential of the emulsion at different EGCG concentrations and amyloid fibrils concentrations,and the absolute values of the potentials were all greater than 40 mV,showing positive values;The increase of EGCG within a specific concentration and the increase of amyloid fibrils concentration can improve the stability of the emulsion.2.Preparation and characterization of HIPEs stabilized by hydrogels encapsulated lutein and its antioxidant effect on oilsExplore the effects of different concentrations of lutein on the particle size,Zeta potential,rheological properties,and microstructure of hydrogel-stabilized HIPEs and hydrogels with different EGCG concentrations different lysozyme amyloid fibrils concentrations antioxidant effects of stable HIPEs on grease.The experimental results showed that the emulsions loading lutein all showed solid rheological properties.The viscoelastic modulus of the high internal phase emulsion decreased with the increase of the lutein concentration,and the stability became worse;The emulsions of lutein all have a highly stacked polyhedral geometry.As the concentration of lutein increases,the average particle size and particle size distribution range of the emulsion increase,and the droplet shape of the emulsion is observed in the laser confocal.The dense and uniform multi-faceted geometric shape approaches the unevenly distributed spherical shape.When the lutein loading is higher than 1 mg/mL,a small number of lutein crystals appear on the surface of the oil drop.There is no significant difference in the Zeta-potential of the emulsion under different loadings of lutein.The absolute value of the potential is greater than 40 mV,which is a positive value.In a specific EGCG concentration range(0 mg/mL～2.5 mg/mL),the emulsion anti-oxidation ability of oils and fats increases with EGCG concentration and amyloid fiber concentration.The increase in the concentration of lutein loaded in HIPEs stabilized by lysozyme amyloid fibril-EGCG hydrogels will reduce emulsion stability.3.Effect of hydrogel stabilized high internal phase emulsion on the stability of luteinHIPEs of loading lutein stabilized by hydrogels with different EGCG concentrations and different amyloid fibrils concentrations are placed under the stress conditions of ultraviolet light,temperature,Fe3+,and hydrogen peroxide to explore the high internal phase.The effect of emulsion on the stability of lutein.The experimental results showed that under all stress conditions,the retention rate of lutein loaded in HIPEs was significantly higher than that of the unencapsulated lutein;Under ultraviolet light,the retention rate of lutein increased significantly with the addition of EGCG,and the concentration of amyloid fibers increased slightly.Among them,the highest retention rate was 67.36%,which was twice that of unembedded lutein;Under the conditions of temperature,Fe3+,and hydrogen peroxide,the retention rate of lutein slightly increases with the addition of EGCG and the concentration of amyloid fibrils.The highest retention rates are 94.39%,97.48%,and 96.40%,respectively.They are twice,three times,and twice as much as the unembedded lutein.HIPEs stabilized by lysozyme amyloid fibril-EGCG hydrogels encapsulate lutein,which can significantly improve the stability of lutein. |
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